Radiation Curable Coating Composition for Metal Adhesion
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Solution Overview
Problem
Current radiation curable coatings for packaging materials, such as metal cans, face issues with inflexibility, poor adhesion, and limited retort resistance due to high shrinkage, and often require high-temperature processes or solvents that release volatile organic compounds (VOCs).
Innovation Solution
The development of radiation curable coating compositions comprising (meth)acrylate functional compounds, including (meth)acrylate functional polyether urethane and adhesion promoting (meth)acrylate compounds, which combine carboxylate and phosphate functional monomers or oligomers, along with poly(meth)acrylate and reactive diluents, to achieve improved adhesion and flexibility without the need for prime coats or high-temperature processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional radiation curable coatings are used, then curing is achieved through UV or EB radiation, but the cured coatings become inflexible and prone to higher levels of shrinkage
Solution Approach 1:
The patent changes the chemical parameters of the coating composition by incorporating specific flexible polymer backbones and controlled crosslink densities. This allows the coating to maintain flexibility after radiation curing while still achieving adequate cure through UV or EB radiation, resolving the contradiction between ease of manufacture and coating stability.
Solution Approach 2:
The patent creates a composite coating system combining flexible polymer matrices with controlled crosslinking agents. This composite structure provides both the flexibility of the polymer backbone and the adhesion/strength of crosslinking, eliminating the inflexibility problem while maintaining radiation curability.
2Ease of manufacture
If conventional radiation curable coatings are used, then curing is achieved, but direct to metal adhesion is inadequate
Solution Approach 1:
The patent introduces adhesion promoters as intermediary substances that bridge the gap between the radiation curable coating and the metal substrate. These promoters contain functional groups that bond to both the coating matrix and the metal surface, enabling direct-to-metal adhesion without requiring separate primer coats or high-temperature flash processes.
Solution Approach 2:
The patent modifies the chemical composition parameters by incorporating specific adhesion-promoting functional groups and optimizing the ratio of crosslinking agents to maintain balance between adhesion strength and coating flexibility, avoiding the need for high-temperature processing.
3Strength
If high temperature flash or prime coat is applied to improve adhesion, then adhesion is enhanced, but process complexity and temperature requirements increase
Solution Approach 1:
The patent extracts and eliminates the need for separate high-temperature flash processes and prime coat applications by incorporating adhesion-promoting functionality directly into the radiation curable coating composition itself. This single-step coating process achieves both adhesion and flexibility without additional process complexity.
Solution Approach 2:
The patent merges the adhesion promoter function, flexibility provision, and radiation curability into a single integrated coating composition. This consolidation eliminates the need for separate process steps like high-temperature flash or prime coat application, reducing process complexity while maintaining adhesion strength.
4Strength
If conventional solvent and waterborne thermoset chemistries are used, then adhesion is achieved, but volatile organic compounds are released
Solution Approach 1:
The patent substitutes the curing mechanism from thermal/chemical curing (which releases VOCs) to radiation curing through UV or EB radiation. This substitution eliminates VOC emissions while maintaining adhesion strength, as the radiation-induced crosslinking occurs without requiring solvent evaporation or high-temperature baking.
Solution Approach 2:
The patent changes the fundamental curing parameter from thermal/chemical activation to radiation activation. This parameter change enables adhesion achievement without VOC release, as the radiation curable composition cures through photopolymerization or electron beam-induced crosslinking rather than through solvent evaporation and thermal curing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The coatings exhibit excellent adhesion to metal substrates, flexibility, and retort resistance, minimizing blush and adhesion loss, while being free from BADGE and NOGE moieties, even with low-energy curing, thus addressing safety, health, and environmental concerns.
Implementation Method 1
radiation curable coating compositions that can provide useful coatings and coated surfaces for packaging materials such as metal cans. Currently available radiation curable coatings such as those that cure through ultra-violet ('UV') radiation or electron beam ('EB') radiation
Data Source
AI summary
Various embodiments of radiation curable coating compositions are provided. In one embodiment, a radiation curable coating composition includes a (meth)acrylate functional compound and an adhesion promoting (meth)acrylate compound. The radiation curable coating composition can also include a (meth)acrylate functional compound, a poly(meth)acrylate and a reactive diluent. The (meth)acrylate functional compound can be made from the reaction of a multifunctional isocyanate, a polyol and a hydroxyl functional (meth)acrylate in the presence of a catalyst.